> How is this opaque data shared between competing resource users?
> What if you have two or more meta-layers? This seems to be not only
> a solution to a problem that doesn't exist, but a foolish solution
> at that.
Well, I assume the problem *does* exist; Jason, Bill, et al may or may not
have lives, but even if they don't I assume they could have found more
enjoyable ways of wasting time than fiddling with the FFS layout.
(I would be interested to see the problem that motivated this solution,
though; 96 bytes of data that an application has to go out of its way to
access, and which gets lost (presumably) if you use generic programs like
"cp" or "tar" to copy the affected files instead of dump and restore?)
> I'd much rather see a well thought out *scaleable* solution.
One problem with scaleable solutions is that they tend to start very big.
Maybe they were trying to just bang in a quick solution to a small problem,
with the opportunity to add a big solution to some as-yet unseen problem
available later...
> As a trivial example, one could design a system of opaque meta-chains,
> the first entry of which was stored in the inode,
I suggested a similar thing to Bill in private email.
I have been amused to see the number of people likening this (or rather,
what this could have been) to MacOS resource forks; I'd have thought
that a UNIX-oriented crowd like this would have regarded the Mac as the
Anti-Computer. ;-) But as Bill pointed out, a MacOS-like resource manager
is not a simple thing (how many resources to you want to have available in
a given file? Few enough that linear search is reasonable? So many that
a whiz-bang extensible hash table in the kernel is reasonable?), and so
one would like to see a distinct set of applications in mind that would
motivate the effort. I'll note that the NTFS (in Windows NT, for those
lucky few who don't know) has the ability to have multiple data streams
associated with a file (like an arbitrary number of MacOS forks, but none
with any OS-imposed layout like the resource fork). However, I'm not
aware of *any* applications that use multiple data streams (and not
surprising -- since any real-world NT application pretty much has to
be willing to run on a FAT filesystem as well). (That's not to say
there are _none_, just that I'm not aware of them.)
Anyway, if I understood Bill's original message, there's a 96-byte area
for "their" application, plus *another* area of uncommitted u_int32_t's
(Bill's message said there were 28 of them, but that's too large; maybe
he meant 8?), some of which are presumably going to be gobbled up for
extending the timestamps to 64 bits, and a pointer to a (first?) block of
ACL info, but that still (I think) leaves a few for some hardy developer
(foolhardy?) to grab a pointer-to-disk-block and run with it. (Just
try to announce it earlier than a week before 1.5 freezes. :-) )